Relationship between foaming properties and solution properties of protein/nonionic surfactant mixtures

The foaming properties of bovine serum albumin (BSA), in the absence and presence of Triton X-100 (TX-100), have been investigated using shaking tests. The results showed that increases in the TX-100 bulk concentration rapidly reduced both foam height and foam stability at TX-100 concentrations below about 0.25 mM, but increased foam height and foam stability at TX-100 concentration above 0.3 mM. The interaction between BSA and TX-100 has been studied using fluorescence spectroscopy. The surfactant appeared to bind to BSA with a low molar ratio (about one surfactant molecule per protein molecule) at concentrations below the critical micelle concentration (CMC); the binding became weaker at concentrations above the CMC. It was confirmed that protein-protein or protein-surfactant interactions had significant influence upon foaming properties of mixed protein/surfactant system.